Influence of cardiac function on image quality in coronary computed tomography angiography

PurposeTo evaluate the correlation between cardiac functional parameters and image quality in coronary computed tomography angiography (CCTA).Material and methodsSixty-six patients who underwent both CCTA and echocardiography were included. The coronary artery attenuation values and contrast-to-noise ratios (CNR) were measured in the proximal right coronary arteries (RCA) and left main (LM) trunk. Then, the averages of the mean values derived from RCA and LM were calculated. The cardiac output (CO), left atrial (LA) volume, and early mitral inflow velocity to mitral annular early diastolic velocity ratio (E/e′) were measured by echocardiography. The relationship of cardiac parameters with arterial attenuation and CNR were assessed by Pearson's correlation, Spearman's rank correlation and multivariable linear regression analysis adjusted for age, gender, body surface area and heart rate.ResultsThe coronary artery attenuation value was negatively correlated with CO (r = −0.30, p = 0.01) and LA volume (r = −0.37, p = 0.002). CNR was negatively correlated with LA volume (r = −0.4, p = 0.001) and E/e′ (r = −0.27, p = 0.03). These associations remained significant in the multivariable analysis.ConclusionCO and diastolic function had an impact on image quality of CCTA. Adjusting CCTA protocol may improve image quality in patients with known diastolic dysfunction or reduced cardiac output.     

Importance of oral fluid intake after coronary computed tomography angiography: An observational study

Background

The prevention of contrast-induced acute kidney injury (AKI) after coronary computed tomography angiography (CCTA) is important because patients referred for CCTA often need further contrast exposure such as an invasive coronary angiography. We aimed to examine the effects of oral volume intake on renal function in patients with preserved renal function referred for CCTA.

Methods

We enrolled 180 patients who were referred for CCTA. The serum creatinine (SCr) and estimated glomerular filtration rate (eGFR) levels were measured before, 24 h, and a mean of 4.8 days after CCTA. The amount of unrestricted oral fluid intake for 24 h was checked. The patients were divided into two groups: 106 subjects with a rise in SCr after CCTA (group A); and 74 without (group B).

Results

Significant correlations were observed between the amount of oral fluid intake and the percentage changes in SCr (%SCr) (r = −0.66, p < 0.0001) as well as the absolute changes in eGFR (ΔeGFR) (r = 0.65, p < 0.0001). The percentage of patients showing hemoglobin-A1c (HbA1c) ≥ 6.5% was greater in group A than in group B (29% vs. 18%, p < 0.001). Patients with HbA1c ≥ 6.5% showed higher %SCr and lower ΔeGFR compared to those without it. Multiple regression analysis revealed that the amount of oral fluid intake was the only independent predictor for a rise in SCr (β = −0.731, p < 0.0001).

Conclusion

Oral volume intake after CCTA is a very simple but important prophylactic procedure for contrast-induced AKI especially in diabetic patients.     

Validation of deep-learning image reconstruction for coronary computed tomography angiography: Impact on noise,image quality and diagnostic accuracy

BackgroundAdvances in image reconstruction are necessary to decrease radiation exposure from coronary CT angiography (CCTA) further, but iterative reconstruction has been shown to degrade image quality at high levels. Deep-learning image reconstruction (DLIR) offers unique opportunities to overcome these limitations. The present study compared the impact of DLIR and adaptive statistical iterative reconstruction-Veo (ASiR-V) on quantitative and qualitative image parameters and the diagnostic accuracy of CCTA using invasive coronary angiography (ICA) as the standard of reference.MethodsThis retrospective study includes 43 patients who underwent clinically indicated CCTA and ICA. Datasets were reconstructed with ASiR-V 70% (using standard [SD] and high-definition [HD] kernels) and with DLIR at different levels (i.e., medium [M] and high [H]). Image noise, image quality, and coronary luminal narrowing were evaluated by three blinded readers. Diagnostic accuracy was compared against ICA.ResultsNoise did not significantly differ between ASiR-V SD and DLIR-M (37 vs. 37 HU, p = 1.000), but was significantly lower in DLIR-H (30 HU, p < 0.001) and higher in ASiR-V HD (53 HU, p < 0.001). Image quality was higher for DLIR-M and DLIR-H (3.4–3.8 and 4.2–4.6) compared to ASiR-V SD and HD (2.1–2.7 and 1.8–2.2; p < 0.001), with DLIR-H yielding the highest image quality. Consistently across readers, no significant differences in sensitivity (88% vs. 92%; p = 0.453), specificity (73% vs. 73%; p = 0.583) and diagnostic accuracy (80% vs. 82%; p = 0.366) were found between ASiR-V HD and DLIR-H.ConclusionDLIR significantly reduces noise in CCTA compared to ASiR-V, while yielding superior image quality at equal diagnostic accuracy.     

How image quality can be improved: our experience with multidetector computed tomography coronary angiography

PURPOSE: The objective of this study was to investigate the factors that may influence image quality on multidetector computed tomography (MDCT) coronary angiography (CA). MATERIALS AND METHODS: Two hundred twenty-four consecutive patients (161 men and 63 women; mean age, 52 years; age range, 34-76 years) evaluated with MDCT CA were included in the study. The evaluation of the quality of the patients' images was mainly based on the contrast material phase (early phase, optimal phase, or late phase) and the level of stepladder artifact (none, acceptable, or unacceptable). In addition, factors such as patient selection, patient preparation, scanning, processing, and steps of analysis, which may be affecting the quality of a final image, were examined independently. RESULTS: Patients who could not achieve sufficient breath-holding despite multiple breath exercises, those with a calcium score of 500 or higher, those with a heart rate greater than 90 bpm after metoprolol administration (because of shortening of the diastolic phase in the most still period), and those whose scanning was not completed were excluded from the study. The results for the remaining 224 patients were evaluated. Based on the contrast phase, there were 66 (29.5%) patients in the first group (early), 93 (41.5%) in the second group (optimal), and 65 (29%) in the third group (late). Among the 224 patients, the images of 152 (67.9%) had no stepladder artifact, those of 67 (29.9%) were of acceptable image quality, and those of 5 (2.2%) were of unacceptable image quality. CONCLUSION: It is important to obtain high-quality images to achieve correct interpretation with coronary artery CT angiography. This study aimed to describe a technique performed on 224 patients based on an array of factors ranging from patient selection to postprocessing. The results show that patient selection, cooperation with the patient, and breath-holding exercises play a very important role in obtaining the best images. In addition, a proper scanning technique (e.g., placement of electrocardiographic electrodes and contrast material phase) and postprocessing (e.g., reconstruction interval) may also contribute to obtaining high-quality images.     

Evaluation of image quality on a per-patient,per-vessel,and per-segment basis by noninvasive coronary angiography with 64-section computed tomography: dual-source versus single-source computed tomography

Purpose  

The purpose of this study was to evaluate the image quality (IQ) of dual-source CT (DSCT) versus single-source CT (SSCT).     

Quantitative parameters of image quality in 64-slice computed tomography angiography of the coronary arteries

We explored quantitative parameters of image quality in consecutive patients undergoing 64-slice multi-detector computed tomography (MDCT) coronary angiography for clinical reasons. Forty-two patients (36 men, mean age 61 +/- 11 years, mean heart rate 63 +/- 10 bpm) underwent contrast-enhanced MDCT coronary angiography with a 64-slice scanner (Siemens Sensation 64, 64 mm x 0.6 mm collimation, 330 ms tube rotation, 850 mAs, 120 kV). Two independent observers measured the overall visualized vessel length and the length of the coronary arteries visualized without motion artifacts in curved multiplanar reformatted images. Contrast-to-noise ratio was measured in the proximal and distal segments of the coronary arteries. The mean length of visualized coronary arteries was: left main 12 +/- 6 mm, left anterior descending 149 +/- 25 mm, left circumflex 89 +/- 30 mm, and right coronary artery 161 +/- 38 mm. On average, 97 +/- 5% of the total visualized vessel length was depicted without motion artifacts (left main 100 +/- 0%, left anterior descending 97 +/- 6%, left circumflex 98 +/- 5%, and right coronary artery 95 +/- 6%). In 27 patients with a heart rate < or = 65 bpm, 98 +/- 4% of the overall visualized vessel length was imaged without motion artifacts, whereas 96+/-6% of the overall visualized vessel length was imaged without motion artifacts in 15 patients with a heart rate > 65 bpm (p < 0.001). The mean contrast-to-noise ratio in all measured coronary arteries was 14.6 +/- 4.7 (proximal coronary segments: range 15.1 +/- 4.4 to 16.1 +/- 5.0, distal coronary segments: range 11.4 +/- 4.2 to 15.9 +/- 4.9). In conclusion, 64-slice MDCT permits reliable visualization of the coronary arteries with minimal motion artifacts and high CNR in consecutive patients referred for non-invasive MDCT coronary angiography. Low heart rate is an important prerequisite for excellent image quality.     

Effect of X-ray tube parameters, iodine concentration, and patient size on image quality in pulmonary computed tomography angiography: a chest-phantom-study

OBJECTIVES: The aim of this phantom study was to evaluate the contrast-to-noise ratio (CNR) in pulmonary computed tomography (CT)-angiography for 300 and 400 mg iodine/mL contrast media using variable x-ray tube parameters and patient sizes. We also analyzed the possible strategies of dose reduction in patients with different sizes. MATERIALS AND METHODS: The segmental pulmonary arteries were simulated by plastic tubes filled with 1:30 diluted solutions of 300 and 400 mg iodine/mL contrast media in a chest phantom mimicking thick, intermediate, and thin patients. Volume scanning was done with a CT scanner at 80, 100, 120, and 140 kVp. Tube current-time products (mAs) varied between 50 and 120% of the optimal value given by the built-in automatic dose optimization protocol. Attenuation values and CNR for both contrast media were evaluated and compared with the volume CT dose index (CTDI(vol)). Figure of merit, calculated as CNR/CTDIvol, was used to quantify image quality improvement per exposure risk to the patient. RESULTS: Attenuation of iodinated contrast media increased both with decreasing tube voltage and patient size. A CTDIvol reduction by 44% was achieved in the thin phantom with the use of 80 instead of 140 kVp without deterioration of CNR. Figure of merit correlated with kVp in the thin phantom (r = -0.897 to -0.999; P < 0.05) but not in the intermediate and thick phantoms (P = 0.09-0.71), reflecting a decreasing benefit of tube voltage reduction on image quality as the thickness of the phantom increased. Compared with the 300 mg iodine/mL concentration, the same CNR for 400 mg iodine/mL contrast medium was achieved at a lower CTDIvol by 18 to 40%, depending on phantom size and applied tube voltage. CONCLUSIONS: Low kVp protocols for pulmonary embolism are potentially advantageous especially in thin and, to a lesser extent, in intermediate patients. Thin patients profit from low voltage protocols preserving a good CNR at a lower exposure. The use of 80 kVp in obese patients may be problematic because of the limitation of the tube current available, reduced CNR, and high skin dose. The high CNR of the 400 mg iodine/mL contrast medium together with lower tube energy and/or current can be used for exposure reduction.     

Relationship of exercise to coronary artery disease extent,severity and plaque type: A coronary computed tomography angiography study

BackgroundWhile exercise has been associated with favorable coronary artery disease (CAD) outcomes, the relationship between endurance exercise levels and CAD findings has not been well explored.PurposeTo evaluate the relationship of endurance exercise to CAD findings by coronary computed tomographic angiography (CCTA).MethodsWe evaluated consecutive patients referred to CCTA who filled out a survey instrument between 2015 and 2017, and who graded their level of weekly endurance exercise as: none, low (1–2 times per week), moderate (3–5 times per week) or high (5–7 times per week); along with the number of hours per week engaged in exercise as: low (<30 min), moderate (1 h) or high (>1–3 h).CCTAanalysis included measurement of maximum per-patient, per-vessel and per-segment stenosis severity, which was judged as minimal (<25%), mild (<50%), moderate (50–70%), and severe (>70%). CAD extent and severity was also summated CADRADS score, plaque burden by segment involvement score (SIS), and non-calcified plaque score (G-score). High-risk plaque (HRP), as defined by the presence of low attenuation plaque, positive arterial remodelling, spotty calcifications and napkin ring signs, was assessed. Finally, coronary artery calcium scores (CCS), as determined by Agatston units, were quantified.ResultsThe study cohort comprised 252 patients (55.3y ±10.1, 39.7% females) with 97 inactives, 87 with low and 68 with moderate-to-high recreational endurance exercise levels (>=3x/week ≥ 1 h) included.Prevalence of subclinical CAD was 57.4%. Prevalence of >50% stenosis was with 13.2% lower at moderate-to-high exercise levels as compared to inactives (p = 0.04). Stenosis severity score (p = 0.04), total (p = 0.036) non-calcified plaque burden were lower (p = 0.026) in athletes, and in the absence of confounding risk factors, the effect strenghtened (SIS and G-score, p = 0.012 and 0.008). There was no difference in the CCS. High-risk plaque prevalence was higher in controls as compared to athletes with moderate-to-high exercise levels (13.4% vs 0%, p = 0.002), and HDL was lower (p < 0.001), respectively. MACE rate was 0%, and ICA rate of >50% stenosis 3.5% at 1 year follow-up.ConclusionRegular moderate-to-high endurance exercise results in lower total and non-calcified plaque burden and less high-risk plaque.     

Non-invasive coronary angiography with 16-slice spiral computed tomography: image quality in patients with high heart rates

The purpose of this study was to assess segment image quality at high heart rates using 16-slice computed tomography and differential reconstruction for major coronary vessels. According to the following protocol, 16-slice CT coronary angiography in 46 patients with a mean heart rate of 86.3+/-11.8 was reconstructed. At three transverse planes, preview series were obtained and motion artifacts evaluated in 5% increments from 0-95% within the cardiac cycle. Relying on image quality in the previews, reconstructions were performed at three z-positions for each patient. Segment image quality was assessed in terms of artifacts and visibility. The effects of heart rate and trigger delay on image quality were analyzed. Optimal image quality was achieved at 25 to 35% of the cardiac cycle for the left circumflex (CX) and right coronary artery (RCA) or 30 to 40% for the left main (LM) and left anterior descending artery (LAD). Sixteen-slice CT and differential reconstruction produced good image quality with a low percentage of motion-degraded proximal and middle segments (8.8%). Grades were 1.5 for the LM, 1.9 for the LAD, 2.0 for the CX and 2.3 for the RCA. At high heart rates, good image quality of the coronary arteries is achieved by 16-slice CT and a sophisticated reconstruction strategy at peak to late systole.     

CT心脑血管一体化成像的图像质量评价

目的 评价双源CT心脑血管一体化成像的图像质量和有效辐射剂量,探讨该方法的关键技术点,为临床提供一种评价心脑血管疾病的无创性影像学方法。方法 前瞻性收集临床同时行冠状动脉和头颈部动脉CT动脉成像（CTA）的连续性患者共493例。根据CT扫描机型分为2组：A组300例,采用第三代双源CT前瞻性心电门控大螺距模式扫描,根据心率进一步分为A1组（n=69,心率≤65次/分）和A2组（n=231,心率>65次/分）;B组193例,采用第二代双源CT前瞻性心电门控大螺距模式扫描,根据心率进一步分为B1组（n=92,心率≤65次/分）和B2组（n=101,心率>65次/分）。分别客观、主观地评价图像质量,计算辐射剂量。计量资料采用独立样本t检验,患者临床资料中的频数参数构成比采用χ2检验,评价图像质量评分一致性采用Cohen Kappa分析。结果 （1）A组和B组患者间年龄（t=0.58,P=0.847）、性别（χ2=1.45,P=0.228）、体重指数（t=1.20,P=0.277）差异均无统计学意义。（2）图像质量客观评价：A组颈总动脉、颈内动脉、大脑中动脉和椎动脉V4段CT值、噪声均低于B组,差异均有统计学意义（t=1.98~4.49,均P < 0.05）,两组患者的主动脉根部CT值（t=0.68,P=0.495）和噪声（t=0.31,P=0.755）差异无统计学意义。（3）图像质量主观评价的一致性Kappa值为0.912。①与B组进行比较,A组的冠状动脉CTA平均图像质量的评分更好（t=0.018,P=0.001）、冠状动脉4级血管基于患者数的不可诊断率更低（χ2=6.63,P=0.014）,且差异均有统计学意义;②与B组进行比较,A组的头颈部CTA评分更好（t=0.013,P=0.004）、头颈部4级血管基于患者数的不可诊断率更低（χ2=4.38,P=0.036）,且差异均有统计学意义;③A组有效辐射剂量为（1.48±0.33）mSv,较B组[（2.14±0.52）mSv]降低了30%,差异有统计学意义（t=14.79,P=0.001）。结论 第三代双源CT心脑血管一体化成像采用不同心率采集不同扫描时间窗的办法,能提供较好的图像质量,且降低了辐射剂量,是一种评价心脑血管疾病的无创性影像学方法。     

Discrepancy between computed tomography coronary angiography and selective coronary angiography in the pre-stenting assessment of coronary lesion length

We aimed to compare the lesion length measured on computed tomography coronary angiography (CT-CA) with the selective coronary angiography (SCA) lesion length measured on quantitative coronary angiography (QCA). Compared with SCA, CT-CA has the advantage of showing the lumen and the atherosclerotic plaque in the arterial wall. This prospective observational study involved 44 coronary lesions. Computed tomography coronary angiography was carried out with an electrocardiogram-gated 16-slice CT before percutaneous coronary intervention. A cardiologist and a radiologist measured CT lesion lengths in consensus, whereas an interventional cardiologist carried out QCA to obtain SCA lesion lengths independently. The median difference of (CT lesion length - SCA lesion length) was 9.84 mm (95%CI: [7.26, 13.34]). The median difference of (stent length - SCA lesion length) was 7.68 mm (95%CI: [6.29, 9.26]); the median difference of (stent length - CT length) was -2.63 mm (95%CI: [-5.80, 0.05]). The mean ratio of stent length to SCA lesion length was 2.07 (95%CI: [1.83, 2.30]). The mean ratio of stent length to CT-CA lesion length was 0.97 (95%CI: [0.83, 1.11]). In the subgroup of drug-eluting stents (17 lesions), the median difference of (stent length - SCA lesion length) was 9.76 mm (95%CI: [6.59, 13.28]); the median difference of (stent length - CT length) was -5.2 mm (95%CI: [-11, 0.5]). The mean ratio of stent length to CT-CA lesion length was 0.93 (95%CI: [0.68, 1.17]). Computed tomography lesion length was substantially longer than SCA lesion length measured by QCA. Routine practice of choosing stent length based on QCA may underestimate the actual length of target lesion. This may lead to incomplete coverage of the target lesion, particularly when drug-eluting stents are used.     

Elongated eccentric soft coronary plaque: major diagnostic pitfall on quantitative coronary angiography overpowered by computed tomography coronary angiography and intravascular ultrasound

We describe a significant left anterior descending coronary lesion in a patient with unstable angina pectoris. This lesion was erroneously underestimated using quantitative coronary angiography; however, CT coronary angiography correctly showed a significant, elongated, eccentric, soft plaque that was later confirmed by repeated quantitative coronary angiography with intravascular ultrasound. As showed, CT coronary angiography may offer a reliable non-invasive alternative to quantitative coronary angiography and intravascular ultrasound by enabling a true 3-D coronary lumenogram combined with plaque detection and characterization.     

Forty-slice spiral computed tomography of the coronary arteries: assessment of image quality and diagnostic accuracy in a non-selected patient population

PURPOSE: To investigate prospectively the image quality and diagnostic accuracy of 40-slice computed tomography (CT) for the detection of hemodynamically significant coronary artery disease (CAD) in a non-selected, consecutive patient cohort. MATERIAL AND METHODS: Forty consecutive patients (28 men, 12 women) underwent both 40-slice CT and conventional invasive coronary angiography (ICA) within 10+/-7 days. The results of both methods were compared on a per-segment and per-patient basis, using ICA as the standard of reference. RESULTS: According to ICA, significant CAD was present in 30/40 patients (75%). Of a total of 545 segments, 43 segments (7.9%) could not be sufficiently evaluated by CT due to motion artifacts in 15 segments (34.9%), small vessel size and suboptimal contrast enhancement in 14 segments (32.6%), severe calcification in 10 segments (23.3%), and opacified adjacent structures such as cardiac veins in four segments (9.3%). Segment-based analysis for detection of significant stenosis >50% yielded an overall sensitivity, specificity, positive predictive value, and negative predictive value of 87%, 99%, 98%, and 95%, respectively. Restricting the assessment to clinically relevant proximal coronary segments led to an increase in sensitivity to 96%, specificity to 99%, and negative predictive value to 99%. Patient-based analysis demonstrated a high negative predictive value (91%) of CT for excluding significant CAD, even when all segments were included in the analysis. CONCLUSION: In a non-selected patient population with a high prevalence of CAD, 40-slice CT demonstrates high diagnostic accuracy in the assessment of significant CAD per patient and per segment.     

CCTA评价冠状动脉狭窄程度与SPECT心肌灌注显像关系的研究

目的：探讨冠心病患者CCTA不同狭窄程度与SPECT MPI间的关系。方法68例患者进行了CCTA和MPI检查,所有患者均行冠状动脉造影。CCTA按管腔狭窄程度分为5个级别,即0,1%~24%,25%~49%,50%~74%,75%~100%。MPI分为正常和灌注缺损(包括可逆缺损和不可逆缺损)。结果68例患者共204根血管纳入分析。以患者为单位进行分析,40例CCTA显示管腔重度狭窄的患者中,29例(72.5%)MPI显示灌注缺损。另外11例(27.5%)CCTA异常的患者心肌灌注 MPI显示正常。在28例CCTA显示未见明显狭窄的患者中,17例(60.1%)显示心肌灌注正常,而另外11例(39.9%)显示灌注缺损。根据CCTA冠状动脉狭窄程度分组,心肌灌注缺损(包括不可逆性灌注缺损和可逆性灌注缺损)出现的比率：0,1%~24%,25%~49%,50%~74%,75%~100%分别为5(27.7%)/18,1(33.3%)/3,5(71.5%)/7,4(50%)/8,25(78.1%)/32。结论冠状动脉狭窄和灌注缺损的不匹配多发生在冠状动脉中度狭窄的患者。在轻度狭窄和重度狭窄的患者中,二者多匹配。冠状动脉中度狭窄的患者应进行CCTA和 MPI联合检查评价冠心病。     

Quantitative parameters to compare image quality of non-invasive coronary angiography with 16-slice, 64-slice and dual-source computed tomography

Multi-slice computed tomography (MSCT) is a non-invasive modality to visualize coronary arteries with an overall good image quality. Improved spatial and temporal resolution of 64-slice and dual-source computed tomography (DSCT) scanners are supposed to have a positive impact on diagnostic accuracy and image quality. However, quantitative parameters to compare image quality of 16-slice, 64-slice MSCT and DSCT are missing. A total of 256 CT examinations were evaluated (Siemens, Sensation 16: n = 90; Siemens Sensation 64: n = 91; Siemens Definition: n = 75). Mean Hounsfield units (HU) were measured in the cavum of the left ventricle (LV), the ascending aorta (Ao), the left ventricular myocardium (My) and the proximal part of the left main (LM), the left anterior descending artery (LAD), the right coronary artery (RCA) and the circumflex artery (CX). Moreover, the ratio of intraluminal attenuation (HU) to myocardial attenuation was assessed for all coronary arteries. Clinical data [body mass index (BMI), gender, heart rate] were accessible for all patients. Mean attenuation (CA) of the coronary arteries was significantly higher for DSCT in comparison to 64- and 16-slice MSCT within the RCA [347 ± 13 vs. 254 ± 14 (64-MSCT) vs. 233 ± 11 (16-MSCT) HU], LM (362 ± 11/275 ± 12/262 ± 9), LAD (332 ± 17/248 ± 19/219 ± 14) and LCX (310 ± 12/210 ± 13/221 ± 10, all p < 0.05), whereas there was no significant difference between DSCT and 64-MSCT for the LV, the Ao and My. Heart rate had a significant impact on CA ratio in 16-slice and 64-slice CT only (p < 0.05). BMI had no impact on the CA ratio in DSCT only (p < 0.001). Improved spatial and temporal resolution of dual-source CT is associated with better opacification of the coronary arteries and a better contrast with the myocardium, which is independent of heart rate. In comparison to MSCT, opacification of the coronary arteries at DSCT is not affected by BMI. The main advantage of DSCT lies with the heart rate independency, which might have a positive impact on the diagnostic accuracy. Christof Burgstahler and Anja Reimann contributed equally to this work     

Noninvasive coronary angiography using 64-slice spiral computed tomography in an unselected patient collective: effect of heart rate, heart rate variability and coronary calcifications on image quality and diagnostic accuracy

OBJECTIVE: The aim of this study was to assess the impact of heart rate, heart rate variability and calcification on image quality and diagnostic accuracy in an unselected patient collective. SUBJECTS AND METHODS: One hundred and two consecutive patients with known or suspected coronary artery disease underwent both 64-MSCT and invasive coronary angiography. Image quality (IQ) was assessed by independent observers using a 4-point scale from excellent (1) to non-diagnostic (4). Accuracy of MSCT regarding detection or exclusion of significant stenosis (>50%) was evaluated on a per segment basis in a modified AHA 13-segment model. Effects of heart rate, heart rate variability, calcification and body mass index (BMI) on IQ and accuracy were evaluated by multivariate regression. IQ and accuracy were further analysed in subgroups of significant predictor variables and simple regression performed to calculate thresholds for adequate IQ. RESULTS: Mean heart rate was 68.2+/-13.3 bpm, mean heart rate variability 11.5+/-16.0 beats per CT-examination (bpct) and median Agatston score 226.5. Average IQ score was 2+/-0.6 whilst diagnostic quality was obtained in 89% of segments. Overall sensitivity, specificity, PPV or NPV was 91.2%, 99.2%, 95.3% or 98.3%. According to multivariate regression, overall IQ was significantly related to heart rate and calcification (P=0.0038; P<0.0001). The effect of heart rate variability was limited to IQ of RCA segments (P=0.018); BMI was not related to IQ (P=0.52). Calcification was the only predictor variable with significant effect on the number of non-diagnostic segments (P<0.0001). In a multivariate regression, calcification was also the single factor with impact on diagnostic accuracy (P=0.0049). CONCLUSION: Whilst heart rate, heart rate variability and calcification all show an inverse correlation to IQ, severe calcium burden remains the single factor with translation of such effect into decrease of diagnostic accuracy.     

Virtual computed tomography colonoscopy: artifacts, image quality and radiation dose load in a cadaver study

The purpose of our study was to evaluate the interdependency of spatial resolution, image reconstruction artifacts, and radiation doses in virtual CT colonoscopy by comparing various CT scanning protocols. A pig's colon with several artificial polypoid lesions was imaged after air insufflation with helical CT scanning using 1-, 3-, and 5-mm collimation, and pitch values varying from 1.0 to 3.0. Virtual endoscopic images and “fly through” sequences were calculated on a Sun Sparc 20 workstation (Navigator Software, GE Medical Systems, Milwaukee, Wis.). Several reconstruction artifacts as well as overall image quality were evaluated by three independent reviewers. In addition, radiation doses for the different CT protocols were measured as multiple-scan average dose using a 10-cm ion chamber and a standard Plexiglass body phantom. Generally, image quality and reconstruction artifacts were less affected by pitch values than by beam collimation. Thus, narrow beam collimation at higher pitch values (e. g. 3 mm/2.0) seems to be a reasonable compromise between quality of virtual endoscopic images and radiation dose load. Received: 4 February 1999; Revised: 16 June 1999; Accepted: 17 June 1999